The present invention relates to an ink ribbon cartridge for a printing machine in particular for a needle printing head fitted on to a movable carriage parallel to the proper guide roll and in which the head can be moved on the carriage perpendicular to its direction of movement.
A machine of the type described is known, in particular for printing on to bank books, in which the ribbon which is wound on to independent spools has a length guided by two ribbon guides arranged at the sides of the paper guide roll, parallel to the roll. The head is fitted with two lateral guides which bring that part of the ribbon placed opposite the typing area close to the roll. The printing head is, moreover, movable on the carriage perpendicular to the roll so as to follow the variations in thickness of the books by keeping constant the distance between the needles, the ribbon and the printing area in every position of the carriage along the line of typing. At each typing cycle, the needles bend the ribbon to maintain a spacing from the printing surface which is independent of the thickness of the book. During the movement of the head in relation to the carriage, the feed mechanism of the ribbon takes care of the ribbon which has to be paid out and that which has to be taken up as the head advances and retracts by keeping the ribbon subjected to a substantially constant tension. While being satisfactory, this solution is, however, somewhat expensive and also results in complications connected with the replacement of the ribbon wound on to independent spools.
A needle printer is also known which uses an ink ribbon cartridge fitted on to the carriage so as to guide a length of ribbon adjacent to the needles of the head in proximity to the paper guide roll. The printing head is fixed on to the carriage and the ribbon is fed by a single direction feed mechanism which is carried on the carriage which, by means of a pair of wires and pulleys is set in motion when the carriage is moved along the line of typing. This solution, which is economic and easy to use cannot, however, be used in printers with movable heads on the carriage, since the ribbon feed mechanism does not permit recovery of the ribbon which has been paid out and, if the carriage were to follow the movement of the head, this latter would require a specific feed mechanism to follow the movement of the cartridge support, thus increasing the mass of the moving parts and the overall cost of the machine.